BFD Front End

typedef bfd

A BFD has type bfd; objects of this type are the cornerstone of any application using BFD. Using BFD consists of making references though the BFD and to data in the BFD.

Here is the structure that defines the type bfd. It contains the major data about the file and pointers to the rest of the data.

     
     struct bfd
     {
       /* A unique identifier of the BFD  */
       unsigned int id;
     
       /* The filename the application opened the BFD with.  */
       const char *filename;
     
       /* A pointer to the target jump table.  */
       const struct bfd_target *xvec;
     
       /* To avoid dragging too many header files into every file that
          includes `bfd.h', IOSTREAM has been declared as a "char *",
          and MTIME as a "long".  Their correct types, to which they
          are cast when used, are "FILE *" and "time_t".    The iostream
          is the result of an fopen on the filename.  However, if the
          BFD_IN_MEMORY flag is set, then iostream is actually a pointer
          to a bfd_in_memory struct.  */
       void *iostream;
     
       /* Is the file descriptor being cached?  That is, can it be closed as
          needed, and re-opened when accessed later?  */
       bfd_boolean cacheable;
     
       /* Marks whether there was a default target specified when the
          BFD was opened. This is used to select which matching algorithm
          to use to choose the back end.  */
       bfd_boolean target_defaulted;
     
       /* The caching routines use these to maintain a
          least-recently-used list of BFDs.  */
       struct bfd *lru_prev, *lru_next;
     
       /* When a file is closed by the caching routines, BFD retains
          state information on the file here...  */
       ufile_ptr where;
     
       /* ... and here: (``once'' means at least once).  */
       bfd_boolean opened_once;
     
       /* Set if we have a locally maintained mtime value, rather than
          getting it from the file each time.  */
       bfd_boolean mtime_set;
     
       /* File modified time, if mtime_set is TRUE.  */
       long mtime;
     
       /* Reserved for an unimplemented file locking extension.  */
       int ifd;
     
       /* The format which belongs to the BFD. (object, core, etc.)  */
       bfd_format format;
     
       /* The direction with which the BFD was opened.  */
       enum bfd_direction
         {
           no_direction = 0,
           read_direction = 1,
           write_direction = 2,
           both_direction = 3
         }
       direction;
     
       /* Format_specific flags.  */
       flagword flags;
     
       /* Currently my_archive is tested before adding origin to
          anything. I believe that this can become always an add of
          origin, with origin set to 0 for non archive files.  */
       ufile_ptr origin;
     
       /* Remember when output has begun, to stop strange things
          from happening.  */
       bfd_boolean output_has_begun;
     
       /* A hash table for section names.  */
       struct bfd_hash_table section_htab;
     
       /* Pointer to linked list of sections.  */
       struct bfd_section *sections;
     
       /* The place where we add to the section list.  */
       struct bfd_section **section_tail;
     
       /* The number of sections.  */
       unsigned int section_count;
     
       /* Stuff only useful for object files:
          The start address.  */
       bfd_vma start_address;
     
       /* Used for input and output.  */
       unsigned int symcount;
     
       /* Symbol table for output BFD (with symcount entries).  */
       struct bfd_symbol  **outsymbols;
     
       /* Used for slurped dynamic symbol tables.  */
       unsigned int dynsymcount;
     
       /* Pointer to structure which contains architecture information.  */
       const struct bfd_arch_info *arch_info;
     
       /* Stuff only useful for archives.  */
       void *arelt_data;
       struct bfd *my_archive;      /* The containing archive BFD.  */
       struct bfd *next;            /* The next BFD in the archive.  */
       struct bfd *archive_head;    /* The first BFD in the archive.  */
       bfd_boolean has_armap;
     
       /* A chain of BFD structures involved in a link.  */
       struct bfd *link_next;
     
       /* A field used by _bfd_generic_link_add_archive_symbols.  This will
          be used only for archive elements.  */
       int archive_pass;
     
       /* Used by the back end to hold private data.  */
       union
         {
           struct aout_data_struct *aout_data;
           struct artdata *aout_ar_data;
           struct _oasys_data *oasys_obj_data;
           struct _oasys_ar_data *oasys_ar_data;
           struct coff_tdata *coff_obj_data;
           struct pe_tdata *pe_obj_data;
           struct xcoff_tdata *xcoff_obj_data;
           struct ecoff_tdata *ecoff_obj_data;
           struct ieee_data_struct *ieee_data;
           struct ieee_ar_data_struct *ieee_ar_data;
           struct srec_data_struct *srec_data;
           struct ihex_data_struct *ihex_data;
           struct tekhex_data_struct *tekhex_data;
           struct elf_obj_tdata *elf_obj_data;
           struct nlm_obj_tdata *nlm_obj_data;
           struct bout_data_struct *bout_data;
           struct mmo_data_struct *mmo_data;
           struct sun_core_struct *sun_core_data;
           struct sco5_core_struct *sco5_core_data;
           struct trad_core_struct *trad_core_data;
           struct som_data_struct *som_data;
           struct hpux_core_struct *hpux_core_data;
           struct hppabsd_core_struct *hppabsd_core_data;
           struct sgi_core_struct *sgi_core_data;
           struct lynx_core_struct *lynx_core_data;
           struct osf_core_struct *osf_core_data;
           struct cisco_core_struct *cisco_core_data;
           struct versados_data_struct *versados_data;
           struct netbsd_core_struct *netbsd_core_data;
           struct mach_o_data_struct *mach_o_data;
           struct mach_o_fat_data_struct *mach_o_fat_data;
           struct bfd_pef_data_struct *pef_data;
           struct bfd_pef_xlib_data_struct *pef_xlib_data;
           struct bfd_sym_data_struct *sym_data;
           void *any;
         }
       tdata;
     
       /* Used by the application to hold private data.  */
       void *usrdata;
     
       /* Where all the allocated stuff under this BFD goes.  This is a
          struct objalloc *, but we use void * to avoid requiring the inclusion
          of objalloc.h.  */
       void *memory;
     };
     
     

Error reporting

Most BFD functions return nonzero on success (check their individual documentation for precise semantics). On an error, they call bfd_set_error to set an error condition that callers can check by calling bfd_get_error. If that returns bfd_error_system_call, then check errno.

The easiest way to report a BFD error to the user is to use bfd_perror.

Type bfd_error_type

The values returned by bfd_get_error are defined by the enumerated type bfd_error_type.

     
     typedef enum bfd_error
     {
       bfd_error_no_error = 0,
       bfd_error_system_call,
       bfd_error_invalid_target,
       bfd_error_wrong_format,
       bfd_error_wrong_object_format,
       bfd_error_invalid_operation,
       bfd_error_no_memory,
       bfd_error_no_symbols,
       bfd_error_no_armap,
       bfd_error_no_more_archived_files,
       bfd_error_malformed_archive,
       bfd_error_file_not_recognized,
       bfd_error_file_ambiguously_recognized,
       bfd_error_no_contents,
       bfd_error_nonrepresentable_section,
       bfd_error_no_debug_section,
       bfd_error_bad_value,
       bfd_error_file_truncated,
       bfd_error_file_too_big,
       bfd_error_invalid_error_code
     }
     bfd_error_type;
     
     

bfd_get_error

Synopsis

     bfd_error_type bfd_get_error (void);
     

bfd_set_error

Synopsis

     void bfd_set_error (bfd_error_type error_tag);
     

bfd_errmsg

Synopsis

     const char *bfd_errmsg (bfd_error_type error_tag);
     

bfd_perror

Synopsis

     void bfd_perror (const char *message);
     

BFD error handler

Some BFD functions want to print messages describing the problem. They call a BFD error handler function. This function may be overridden by the program.

The BFD error handler acts like printf.

     
     typedef void (*bfd_error_handler_type) (const char *, ...);
     
     

bfd_set_error_handler

Synopsis

     bfd_error_handler_type bfd_set_error_handler (bfd_error_handler_type);
     

bfd_set_error_program_name

Synopsis

     void bfd_set_error_program_name (const char *);
     

bfd_get_error_handler

Synopsis

     bfd_error_handler_type bfd_get_error_handler (void);
     

bfd_archive_filename

Synopsis

     const char *bfd_archive_filename (bfd *);
     

Symbols

bfd_get_reloc_upper_bound

Synopsis

     long bfd_get_reloc_upper_bound (bfd *abfd, asection *sect);
     

bfd_canonicalize_reloc

Synopsis

     long bfd_canonicalize_reloc
        (bfd *abfd, asection *sec, arelent **loc, asymbol **syms);
     

The syms table is also needed for horrible internal magic reasons.

bfd_set_reloc

Synopsis

     void bfd_set_reloc
        (bfd *abfd, asection *sec, arelent **rel, unsigned int count);
     

bfd_set_file_flags

Synopsis

     bfd_boolean bfd_set_file_flags (bfd *abfd, flagword flags);
     

Possible errors are:

• bfd_error_wrong_format - The target bfd was not of object format.
• bfd_error_invalid_operation - The target bfd was open for reading.
• bfd_error_invalid_operation - The flag word contained a bit which was not applicable to the type of file. E.g., an attempt was made to set the D_PAGED bit on a BFD format which does not support demand paging.

bfd_get_arch_size

Synopsis

     int bfd_get_arch_size (bfd *abfd);
     

Returns
Returns the arch size in bits if known, -1 otherwise.

bfd_get_sign_extend_vma

Synopsis

     int bfd_get_sign_extend_vma (bfd *abfd);
     

Returns
Returns 1 if the target architecture is known to sign extend addresses, 0 if the target architecture is known to not sign extend addresses, and -1 otherwise.

bfd_set_start_address

Synopsis

     bfd_boolean bfd_set_start_address (bfd *abfd, bfd_vma vma);
     

Returns
Returns TRUE on success, FALSE otherwise.

bfd_get_gp_size

Synopsis

     unsigned int bfd_get_gp_size (bfd *abfd);
     

bfd_set_gp_size

Synopsis

     void bfd_set_gp_size (bfd *abfd, unsigned int i);
     

bfd_scan_vma

Synopsis

     bfd_vma bfd_scan_vma (const char *string, const char **end, int base);
     

If the value would overflow, the maximum bfd_vma value is returned.

bfd_copy_private_bfd_data

Synopsis

     bfd_boolean bfd_copy_private_bfd_data (bfd *ibfd, bfd *obfd);
     

• bfd_error_no_memory - Not enough memory exists to create private data for obfd.

     #define bfd_copy_private_bfd_data(ibfd, obfd) \
          BFD_SEND (obfd, _bfd_copy_private_bfd_data, \
                    (ibfd, obfd))
     

bfd_merge_private_bfd_data

Synopsis

     bfd_boolean bfd_merge_private_bfd_data (bfd *ibfd, bfd *obfd);
     

• bfd_error_no_memory - Not enough memory exists to create private data for obfd.

     #define bfd_merge_private_bfd_data(ibfd, obfd) \
          BFD_SEND (obfd, _bfd_merge_private_bfd_data, \
                    (ibfd, obfd))
     

bfd_set_private_flags

Synopsis

     bfd_boolean bfd_set_private_flags (bfd *abfd, flagword flags);
     

• bfd_error_no_memory - Not enough memory exists to create private data for obfd.

     #define bfd_set_private_flags(abfd, flags) \
          BFD_SEND (abfd, _bfd_set_private_flags, (abfd, flags))
     

Other functions

Description
The following functions exist but have not yet been documented.

     #define bfd_sizeof_headers(abfd, reloc) \
            BFD_SEND (abfd, _bfd_sizeof_headers, (abfd, reloc))
     
     #define bfd_find_nearest_line(abfd, sec, syms, off, file, func, line) \
            BFD_SEND (abfd, _bfd_find_nearest_line, \
                      (abfd, sec, syms, off, file, func, line))
     
     #define bfd_debug_info_start(abfd) \
            BFD_SEND (abfd, _bfd_debug_info_start, (abfd))
     
     #define bfd_debug_info_end(abfd) \
            BFD_SEND (abfd, _bfd_debug_info_end, (abfd))
     
     #define bfd_debug_info_accumulate(abfd, section) \
            BFD_SEND (abfd, _bfd_debug_info_accumulate, (abfd, section))
     
     #define bfd_stat_arch_elt(abfd, stat) \
            BFD_SEND (abfd, _bfd_stat_arch_elt,(abfd, stat))
     
     #define bfd_update_armap_timestamp(abfd) \
            BFD_SEND (abfd, _bfd_update_armap_timestamp, (abfd))
     
     #define bfd_set_arch_mach(abfd, arch, mach)\
            BFD_SEND ( abfd, _bfd_set_arch_mach, (abfd, arch, mach))
     
     #define bfd_relax_section(abfd, section, link_info, again) \
            BFD_SEND (abfd, _bfd_relax_section, (abfd, section, link_info, again))
     
     #define bfd_gc_sections(abfd, link_info) \
            BFD_SEND (abfd, _bfd_gc_sections, (abfd, link_info))
     
     #define bfd_merge_sections(abfd, link_info) \
            BFD_SEND (abfd, _bfd_merge_sections, (abfd, link_info))
     
     #define bfd_discard_group(abfd, sec) \
            BFD_SEND (abfd, _bfd_discard_group, (abfd, sec))
     
     #define bfd_link_hash_table_create(abfd) \
            BFD_SEND (abfd, _bfd_link_hash_table_create, (abfd))
     
     #define bfd_link_hash_table_free(abfd, hash) \
            BFD_SEND (abfd, _bfd_link_hash_table_free, (hash))
     
     #define bfd_link_add_symbols(abfd, info) \
            BFD_SEND (abfd, _bfd_link_add_symbols, (abfd, info))
     
     #define bfd_link_just_syms(sec, info) \
            BFD_SEND (abfd, _bfd_link_just_syms, (sec, info))
     
     #define bfd_final_link(abfd, info) \
            BFD_SEND (abfd, _bfd_final_link, (abfd, info))
     
     #define bfd_free_cached_info(abfd) \
            BFD_SEND (abfd, _bfd_free_cached_info, (abfd))
     
     #define bfd_get_dynamic_symtab_upper_bound(abfd) \
            BFD_SEND (abfd, _bfd_get_dynamic_symtab_upper_bound, (abfd))
     
     #define bfd_print_private_bfd_data(abfd, file)\
            BFD_SEND (abfd, _bfd_print_private_bfd_data, (abfd, file))
     
     #define bfd_canonicalize_dynamic_symtab(abfd, asymbols) \
            BFD_SEND (abfd, _bfd_canonicalize_dynamic_symtab, (abfd, asymbols))
     
     #define bfd_get_dynamic_reloc_upper_bound(abfd) \
            BFD_SEND (abfd, _bfd_get_dynamic_reloc_upper_bound, (abfd))
     
     #define bfd_canonicalize_dynamic_reloc(abfd, arels, asyms) \
            BFD_SEND (abfd, _bfd_canonicalize_dynamic_reloc, (abfd, arels, asyms))
     
     extern bfd_byte *bfd_get_relocated_section_contents
       (bfd *, struct bfd_link_info *, struct bfd_link_order *, bfd_byte *,
        bfd_boolean, asymbol **);
     
     

bfd_alt_mach_code

Synopsis

     bfd_boolean bfd_alt_mach_code (bfd *abfd, int alternative);
     

     struct bfd_preserve
     {
       void *marker;
       void *tdata;
       flagword flags;
       const struct bfd_arch_info *arch_info;
       struct bfd_section *sections;
       struct bfd_section **section_tail;
       unsigned int section_count;
       struct bfd_hash_table section_htab;
     };
     
     

bfd_preserve_save

Synopsis

     bfd_boolean bfd_preserve_save (bfd *, struct bfd_preserve *);
     

bfd_preserve_restore

Synopsis

     void bfd_preserve_restore (bfd *, struct bfd_preserve *);
     

bfd_preserve_finish

Synopsis

     void bfd_preserve_finish (bfd *, struct bfd_preserve *);
     

bfd_get_mtime

Synopsis

     long bfd_get_mtime (bfd *abfd);
     

bfd_get_size

Synopsis

     long bfd_get_size (bfd *abfd);
     

The initial motivation for, and use of, this routine is not so we can get the exact size of the object the BFD applies to, since that might not be generally possible (archive members for example). It would be ideal if someone could eventually modify it so that such results were guaranteed.

Instead, we want to ask questions like "is this NNN byte sized object I'm about to try read from file offset YYY reasonable?" As as example of where we might do this, some object formats use string tables for which the first sizeof (long) bytes of the table contain the size of the table itself, including the size bytes. If an application tries to read what it thinks is one of these string tables, without some way to validate the size, and for some reason the size is wrong (byte swapping error, wrong location for the string table, etc.), the only clue is likely to be a read error when it tries to read the table, or a "virtual memory exhausted" error when it tries to allocate 15 bazillon bytes of space for the 15 bazillon byte table it is about to read. This function at least allows us to answer the question, "is the size reasonable?".

• Memory Usage:
• Initialization:
• Sections:
• Symbols:
• Archives:
• Formats:
• Relocations:
• Core Files:
• Targets:
• Architectures:
• Opening and Closing:
• Internal:
• File Caching:
• Linker Functions:
• Hash Tables: